This application relates to a separate connector system for releasably connecting conductive paths of a flexible circuit to closely packed conductive pads or posts.
In electrical systems, flexible printed circuits are employed as electrical jumpers or cable for interconnecting rows of terminal pins or pads of printed circuit boards. A connector, mounted to one or both ends of the jumper, has typically been formed with a set of electrical receptacles or sockets which are designed to receive the terminal posts or contact the pads on the printed circuit board.
In today""s electronics market, manufacturers are placing emphasis on increasing their product""s reliably and reducing assembly costs to remain competitive. A primary focus of each manufacturer is to reduce the cost and increase the circuit density associated with interconnecting the sub-assemblies and components found within its products. Another emerging focus in today""s electronics market is to pack more electronic functions into smaller packages. This means higher density modules, each requiring multiple high density interconnections to other modules.
Connector manufacturers have not kept pace with today""s market needs. Simply stated, conventional connector technology cannot accommodate today""s high-density requirements. Most existing connectors consist of individual stamped contacts assembled into a molded plastic housing. The physical size required to manufacture an acceptable spring contact eliminates this technology in high-density circuits. For the last thirty years, electronic systems have been designed around conventional connector technology. Connector manufacturers have effectively led this market, and system designers gladly followed, because these connectors satisfied their needs. This cannot continue as significant events are combining to change the role of connectors forever, including a new generation of chips that are driving PC board manufacturers to produce boards with conductors having 0.015xe2x80x3 wide contacts on 0.025xe2x80x3 or less centers. These boards must be interconnected to other modules or to the outside world and will require a high-density connector and interconnect cable.
These key events have led to development of the high-density connector system of the present invention.
U.S. Pat. No. 4,740,867 discloses a connection system for connecting a flexible circuit having a row of printed contact areas to a PC board having a corresponding row of terminal posts employs a connector having a housing with a bottom wall and a pair of side walls at least one of which is movable with respect to the other. A row of post-receiving passages are present in the bottom wall which passages are arranged to receive the posts of the PC board. An edge margin of the flexible circuit is clamped between the housing side walls so that the contact areas thereon are aligned with the passages in the housing bottom wall and a set of springs positioned inside the housing flexes the circuit edge margin so that when the movable housing side wall is in its closed position, the row of contact areas overhang the passages in the housing bottom wall. Consequently, when the connector housing is impaled on the printed PC board posts, the posts project into the housing and are resiliently engaged by corresponding ones of the flexible circuit conductive areas.
While providing a connector arrangement for closely spaced posts on printed circuit boards, the connector of U.S. Pat. No. 4,740,867 has significant drawbacks involving the use of expensive fixtures to facilitate assembly of the connector and, even then, involves difficult assembly techniques. Further this connector has a component retaining shell or housing, which is prone to failure due to pressures applied when the posts are inserted into the connector. Additional discussion of the limitations of the connector of U.S. Pat. No. 4,740,867 will be found in the inventor""s notes forming a part of this document.
Subsequent to the development of the connector disclosed in U.S. Pat. No. 4,740,867, one of the inventors of the present application developed, and patented in U.S. Pat. No. 5,350,319, an edge connector for connecting flexible circuit conductors to contact pads of a PC board edge connector having a snap together housing of modular design having resiliently biased flexible circuits for contacting the pads, an alignment arrangement for alignment of the conductors and pads, protection for the free end regions of the flexible circuits and strain relief features, the connector being usable with conductors spaced 0.012xe2x80x3 or less apart, and being easily assembled and disassembled.
The connector of U.S. Pat. No. 5,350,319 consists of a multi-part housing comprising two modules in mirror image disposed about two inner modules also in mirror image housing contact enhancing springs and contacts of a flexible circuit for engagement with contacts on both sides of an edge connector of printed circuit board, all of which are connected together by a housing 6 which is snapped over the outer modules. Although this arrangement improves ease of assembly, relative to U.S. Pat. No. 4,740,867 and also, permits disassembly of the connector, if and when needed, the structure is still complex and assembly is still difficult and expensive.
It is an object of the present invention to provide a separable connector system for reliably and releasably connecting the conductive circuit paths of a flexible circuit to closely packed (high density) conductive pads or posts of a PC board in a way that does not require solder, crimping or welding operations in order to interconnect the two circuits, the connector system providing accurate registration to ensure reliable desired connection.
A further object is to provide a connector system which can be formed as an inexpensive structure, is relatively easy and inexpensive to make in quantity and can be mounted to the end of a flexible circuit without requiring any tool and which can be readily connected to and aligned with contact pads on the face of a printed circuit board.
The present invention comprises a one-piece molded housing, open at one end to receive connector components, and defining, at an opposed end, at least one aperture for receiving a post or edge connector of a printed circuit board for connection to conductive contact areas of a flexible circuit extending into the connector. A flat contact biasing spring is supported, by holes, on posts of the connector, which are formed on a sled designed to be inserted into the open end of the one-piece housing during assembly so that the posts engage and are located by the one-piece housing with a resilient detents engaging an opening in the housing to locate the sled in place after assembly. The flexible circuit extends over the posts on which the spring is mounted and engages strain relief posts on the sled adjacent the open end of the housing.
More specifically, the invention provides a connector for connecting conductors of a flexible circuit to conductive elements comprising a plastic shell defining at least one opening for access of the conductive elements into the connecter for contact with the conductors, the conductors being located in the connector and biased for the conductive contact with the conductive elements by a flat contact biasing spring, the flexible circuit and spring being mounted to a sled, the sled being supported in the housing by pins and a detent on the sled engaging a detent receiving opening in the housing.
Preferably: the spring comprises a plurality of parallel spring tines supported by a cross-member interconnecting one end of the tines, the cross-member defining openings engaging posts projecting from a spring support and orientation controlling pad of the sled; the available spring tine deflection is determined by a spring engaging surface of the pad relative to the sled and the sled has spacer plates with detents to firmly hold the cross-member against the pad; the pins comprise a plurality of mounting pins engaging openings in an end portion of the flexible circuit between the conductors thereof, the flexible circuit also having openings engaging the posts to provide strain relief for the flexible circuit whereby the flexible circuit is supported on the sled with the spring therebetween and the conductors exposed for contact with the conductive elements; the shell has openings, adjacent the at least one opening, to receive the mounting pins to align the sled and hold the end of the flexible circuit captive on the mounting pins; the shell has slots to receive ends of the posts to hold the flexible circuit captive on the posts; and the shell has a substantially rectangular interior cavity and the spacer plates are sized to engage wall of the cavity to locate the sled, spring and flexible circuit in the shell in coordination with the detent on the sled engaging the detent receiving opening.
Also according to the invention a method of producing a connector for connection to conductive elements comprises: a) providing a one-piece, plastic housing having opposed first and second ends, the first end incorporating openings for receiving the conductive elements and the second end being open for the insertion of interior features of the connector. b) providing a sled capable of insertion in the second end of the housing and including alignment and retention features for aligning and retaining the sled in the housing; c) mounting a conductor carrying flexible circuit to retaining features and strain relief features formed on the sled; d) mounting a flexible circuit biasing flat spring on the retaining features of the sled in a location to bias contacts of the printed flexible circuit into conductive contact with the conductive printed circuit features when inserted through the opening in the first end of the housing, and e) inserting the sled with the flexible circuit and spring mounted thereon through the open second end of the housing to engage the alignment and retaining feature of the sled with the housing to locate the sled within the housing to provide an assembled connector complete with the interior features thereon.